A multimeter or a multitester, also known as a volt/ohm meter or VOM, is an electronic measuring instrument that combines several measurement functions into one device. A typical multimeter may include features such as the ability to measure voltage, current, and resistance. There are two main categories of multimeters, they are typically digital multimeters (DMM) and analog multimeters.
Modern multimeters are often digital due to their accuracy, durability, and extra features. In regard to a DMM, the signal under test is converted to a voltage, and an amplifier with electronically controlled gain preconditions the signal. A DMM displays the quantity measured as a number, which prevents parallax errors.
A DMM may be a hand-held device useful for basic fault finding and field service work, or a bench instrument which can measure to a very high degree of accuracy. The DMM is used to troubleshoot electrical problems in a wide array of industrial and household devices such as batteries, motor controls, appliances, power supplies, and wiring systems.
Hand-held DMMs use a battery or batteries for continuity and resistance readings at the very least, and the battery may also power a DMM or an amplifier in an FET-VOM. This allows the DMM to test a device that is disconnected from a main power source, by supplying its own low voltage for the test. It is one of the most important safety features of the DMM. A 1.5 volt AA battery is typical; more sophisticated meters with added capabilities additionally use a 9 volt battery for some types of readings, or higher-voltage batteries for higher resistance testing. DMMs intended for testing in hazardous locations or for use on blasting circuits may require use of a manufacturer-specified battery to maintain their safety rating.
Modern DMMs may have an embedded computer, which provides a wealth of convenience features. Modern DMMs are often interfaced with a personal computer by RS-232 connections, USB, or an instrument bus such as IEEE-488. The interface allows the computer to record measurements as they are made. Some DMM's can store measurements and upload them to a computer.
However, using an actual wire connection between a DMM and a computer, such as an RS-232 or USB, is limited because the DMM and device under test must be in close proximity to the computer because of the wire connection. This limits the use of a DMM when it is physically impossible to have the device under test in proximity to the computer such that the wire connection can be made between the DMM and the computer.
Accordingly, there exists a need for a DMM which is able to record desired measurements or parameters of a device under test, and communicate wirelessly with a computer, allowing the computer to record the measurements or parameters.